#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    int numDistinct(string s, string t) {
        int n = s.size(), m = t.size();
        s = " " + s;
        t = " " + t;
        vector<vector<double>> dp(m + 1, vector<double>(n + 1, 0));
        for (int i = 0;i <= n;i++) dp[0][i] = 1;
        for (int i = 1;i <= m;i++)
        {
            for (int j = 1;j <= n;j++)
            {
                dp[i][j] = t[i] == s[j] ? dp[i - 1][j - 1] + dp[i][j - 1] : dp[i][j - 1];
            }
        }
        return dp[m][n];
    }
};